Correct isRunning() behavior for AnimatorSet

isRunning() for an Animator indicates whether an animator has gone
past its start delay and not yet finished. As a subclass of Animator,
AnimatorSet should follow the same principle. The implemention prior
to this CL returns whether any child animation is running, which is
inconsistent with the javadoc for isRunning() and general behavior
for Animator.

Change-Id: Iece814dfcd609ee292dbc00bd55dc64c7bda8e57
diff --git a/core/java/android/animation/AnimatorSet.java b/core/java/android/animation/AnimatorSet.java
index 5b88c8e..16f825d 100644
--- a/core/java/android/animation/AnimatorSet.java
+++ b/core/java/android/animation/AnimatorSet.java
@@ -408,15 +408,18 @@
 
     /**
      * Returns true if any of the child animations of this AnimatorSet have been started and have
-     * not yet ended.
-     * @return Whether this AnimatorSet has been started and has not yet ended.
+     * not yet ended. Child animations will not be started until the AnimatorSet has gone past
+     * its initial delay set through {@link #setStartDelay(long)}.
+     *
+     * @return Whether this AnimatorSet has gone past the initial delay, and at least one child
+     *         animation has been started and not yet ended.
      */
     @Override
     public boolean isRunning() {
         int size = mNodes.size();
         for (int i = 0; i < size; i++) {
             Node node = mNodes.get(i);
-            if (node != mRootNode && node.mAnimation.isRunning()) {
+            if (node != mRootNode && node.mAnimation.isStarted()) {
                 return true;
             }
         }